Characterization and evaluation of cocoa (Theobroma cacao L.) pod husk as a renewable energy source

In Colombia, the cocoa pod husk (CPH) is expected to reach 2 100 000 t year^-1 in 2021 which is usually burned or left over for decomposing outdoors at the plantations without any environmental control. Therefore, this study evaluated the energetic potential of CPH obtained after the initial processing of this fruit (Theobroma cacao L.). Three biological materials were analyzed: clone CCN-51 (CPH₁), clone ICS-39 (CPH₂) and a hybrid (CPH₃), which present high yield and number of fruits per tree. The samples were examined by using different characterization techniques for raw biomass and ashes; in addition to the ultimate, proximate and heating value analyses, different fouling indexes were determined in order to estimate the phenomena of solids formation inside the reactor when combustion or gasification is used as a thermochemical valorization process. The Colombian CPHs contain relatively homogeneous levels of C, H and O, but very heterogeneous ash contents (1.4 to 12.9 wt %). The three studied samples showed high content of K₂O in ashes (67 to 74 wt %). The higher heating value (HHV) ranged from 15 395 to 16 670 kJ kg^-1. Furthermore, the fouling index and the fusibility analysis suggest the appearance of agglomeration and sintering phenomena when CPH is used as a fuel. The gasification is proposed as the process with major possibilities for the energetic use of CPH. CPH₁ sample seems to allow a more stable and flexible operation, as compared to CPH₂ and CPH₃.